Posted: May 29, 2012 Topics: Engineering & Science
A second earthquake has hit northern Italy, this time killing at least 15 people. The 5.8 magnitude quake comes just nine days after last Sunday's 6.0 tremblor, which killed seven people. Scientists believe the two events are connected.
Andrew Newman and Zhigang Peng are researchers in the School of Earth and Atmospheric Sciences. They discuss Italy's earthquake history, why the quakes aren't uncommon and why they're so deadly.
Why Does Italy Have Earthquakes?
Italy is a bit of an anomaly, seismically speaking. In northern Italy (northward of Rome), activity stems from a failed subduction zone that formed a substantial mountain belt that runs the length of the country (similar to the Appalachians, but much younger). The mountains themselves are unstably high, and are failing in many earthquakes, usually smaller than magnitude 6. This describes most of the seismicity in the country. However, the recent events are a little offset from this normal chain of seismicity and may represent a combination of local off-axis gravitationally driven compression and more broad-scale compression of the region due to the collision of Africa into Eurasia.
In the near future, we can certainly expect more aftershocks and regionally triggered events. In the long-term, Italy will likely continue its trend of experiencing a magnitude 5.5 or greater about once a year.
Italy's Seismic History
Earthquakes are quite common in Italy. Many of them are deadly because the country has many old buildings that cannot withstand the quakes.
In 1693, an 8.0 magnitude event generated a large tsunami that destroyed numerous towns along Sicily's east coast. Sicly was rocked again In 1908 during's Europe's deadliest documented earthquake. A 7.2 magnitude quake hit the town of Messina and caused a local tsunami that killed more than 100,000 people.
More recently, in 2009, the magnitude 6.3 L'Aquila earthquake occurred in the region of Abruzzo in central Italy. Scientists were accused of not being able to predict that event, despite obvious foreshock sequences.